1. Field of the Invention
This invention relates to reinforcing roadways with a prefabricated reinforcing composite, and primarily to reinforcing asphaltic concrete overlays on Portland concrete or other underlying pavements to prevent cracks and other defects, which had previously appeared in the underlying pavement, from reappearing in the overlay. Thermal expansion or contraction is the primary cause of such cracks in the underlayment reappearing in the overlay. This phenomena is generally referred to as "reflective" cracks. The prefabricated reinforcing composite is a resin-impregnated, semi-rigid, open grid of continuous fiberglass filaments. The crosswise and lengthwise intersections of the grid are stitched together or otherwise fixedly connected. In use, the underlying pavement is coated with an asphaltic tack-coat; the semi-rigid, open grid of this invention is then unrolled over the tack-coat; and an asphaltic mixture overlay is applied. Composites of asphaltic materials and fiberglass have shown superior resistance to reflective cracking and other defects.
2. Description of the Prior Art
Various methods and composites for reinforcing asphaltic roads and overlays have been proposed. U.S. Pat. No. 2,115,667 of Ellis (1937) refers to the use of flexible, woven, tape-like strips or ribbons of fiberglass, 1/2" to 1" wide, which are interwoven at right angles to produce a netting with openings ranging from one to three inches square. These interwoven, flexible tapes are laid on a bed of asphalt and tied together at their intersections by means of wire staples. Another layer of molten asphalt is laid on top of the tapes, followed by crushed stone and a top coat of asphalt. The art has also used narrow strips (4 to 44 inches wide) of a loosely woven fabric made of flexible fiberglass roving (weighing 24 ounces per square yard) in the repair of cracks in pavement. These are not impregnated with resin, and do not have grid-like openings. They are laid down on top of a tack coat, followed by application of asphaltic concrete, but they are too expensive and too flexible to be practical to lay over substantial portions of a roadway and, because of their flexibility, like the unimpregnated structures of Ellis, would be difficult to handle if installed over substantial portions of a road where they could be subjected to traffic from paving vehicles and personnel as the overlayment is put down. Also the lack of adhesion between underlayment and overlying layers is a problem because of the essentially closed nature of the fabric.
Also in the prior art are rigid plastic grids, such as shown in U.S. Pat. No. 4,168,924. These have the disadvantage that they cannot be continuously unrolled and are therefore difficult to install, and while they may use fiberglass as a filler for the plastic, they do not have the strength and other desirable characteristics of continuous filament fiberglass strands.